Speaker: Dr. Olivier Delaire, Duke University

Speaker:  Dr. Olivier Delaire, Duke University

Title:  Atomic Dynamics in Energy and Functional Materials:  Vibrations, Diffusion, and Phase Transitions

Abstract:  Probing and understanding atomic motions in solids is needed to refine microscopic theories of transport and thermodynamics, in order to design improved materials. In particular, the behavior of atomic vibrations (phonons) is key to rationalize numerous functional properties, ranging from multiferroics for information processing and superionics for safer solid batteries, to thermoelectrics for cooling or waste-heat harvesting. Yet, textbook models of lattice dynamics often fall short in real materials. For instance, near phase transitions associated with lattice instabilities, strong anharmonic effects disrupt the conventional quasiharmonic phonon gas model. Large vibrational amplitudes also renormalize the electronic structure via the electron-phonon interaction. This presentation will highlight the importance of atomic dynamics in multiple classes of materials, including halide perovskite photovoltaics [1], thermoelectrics [2,3], and superionic conductors [4-6]. We use state-of-the-art neutron and x-ray scattering techniques to probe atomic structure and dynamics, from phonon propagation to understand thermal transport, to ionic hopping to understand solid-state diffusion. Our complementary first-principles and machine-learning simulations enable the quantitative rationalization of experiments, and identify underlying principles and descriptors enabling future materials design. 

[1] T. Lanigan-Atkins*, X. He* et al. “Two-dimensional overdamped fluctuations of soft perovskite lattice in CsPbBr3”, Nature Materials (2021), https://doi.org/10.1038/s41563-021-00947-y

[2] J. Ding et al. “Anharmonic phonons and origin of ultralow thermal conductivity in Mg3Sb2 and Mg3Bi2”, Science Advances 7:eabg1449 (2021). https://doi.org/10.1126/sciadv.abg1449 

[3] T. Lanigan-Atkins*, S. Yang* et al. “Extended anharmonic collapse of phonon dispersions in SnS and SnSe“, Nature Communications 11 (1), 1-9 (2020). https://doi.org/10.1038/s41467-020-18121-4   

[4] J. L. Niedziela et al. “Selective Breakdown of Phonon Quasiparticles across Superionic Transition in CuCrSe2”, Nature Physics, 15, 73–78 (2019). https://doi.org/10.1038/s41567-018-0298-2 

[5] J. Ding et al. “Anharmonic lattice dynamics and superionic transition in AgCrSe2”, PNAS 117 (8) 3930-3937 (2020). https://doi.org/10.1073/pnas.1913916117 

[6] M. Gupta et al. “Fast Na diffusion and anharmonic phonon dynamics in superionic Na3PS4”, Energy and Environmental Science (2021), https://doi.org/10.1039/D1EE01509E 

Bio:  Olivier Delaire obtained a PhD in Materials Science from Caltech (2006). Following a postdoc at Caltech, he became Clifford Shull Fellow at Oak Ridge National Lab (2008), and subsequently Staff Researcher in the Materials Science and Technology Division at ORNL (2012-2015). In 2016, he became Associate Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science at Duke University. The Delaire group investigates atomic dynamics in a wide range of materials for energy applications, sensing, and information storage. 

Website: delaire.pratt.duke.edu